Silicone polymers have found increasing utility in a variety of applications. Resistance to high temperature, UV light stability, low temperature flexibility and dielectric strength are all properties of silicone polymers which contribute to this trend. Notably, silicone polymers are employed as coatings, for example as release coatings or paints; as sealants, for example in construction expansion joints or in automotive; as potting compounds for electronic components; as gaskets; etc.
Moisture cured silicone polymers find the greatest utility in terms of volume use. Generally, these silicone polymers are applied and simply allowed to cure by diffusion of atmospheric moisture into the polymer Understandably, under these cure conditions, minutes to hours are required before the moisture cured silicone polymer is "tack free", that is, sufficiently cured on the surface to permit further contact. Days are required before any but a thin layer of moisture cured silicone polymer is cured throughout.
One method to speed cure time of moisture cured silicone polymers is to incorporate a source of water immediately before application. With this method, mass transfer hinderances of water from the atmosphere onto the surface and into the bulk of silicone polymer is considerably reduced. Likewise, tack free time and cure times are also much reduced. However, a mixing step before application is required and while tack free time is reduced, it is still considerable for some applications.
U.S. Pat. No. 4,528,081 to Lien, et al., produces a moisture cured silicone polymer which is substituted with acrylic groups and is mixed with a photocatalyst. Thus, the composition therein can be rendered tack free with brief exposure to UV light and continue curing as a moisture cured silicone polymer. One drawback to this dual curable composition is the oxygen inhibition of acrylic groups under UV light exposure.
It is an object of the present invention to produce a dual curable silicone polymer composition.
It is yet another object of this invention to produce a dual curable composition of moisture cured silicone polymer utilizing UV light sensitive epoxy groups.
It is still another object of the present invention to produce a dual curable composition exhibiting no oxygen inhibition.